Pressure measuring guide wire

ABSTRACT

The pressure measuring guide wire comprises an elongated flexible shaft with a lumen extending therethrough. The lumen is surrounded by a wall forming the shaft and the distal portion of which is provided with slots for pressure medium entry. The distal portion has a thickness, greater than the thickness of the proximal area of the shaft. A coil surrounds the proximal area of the shaft to compensate the difference in kinking resistance between the proximal and distal areas of the shaft.

BACKGROUND OF THE INVENTION

This invention relates to a pressure measuring guide wire comprising anelongated flexible shaft with a proximal portion, a distal portion, alumen extending through the shaft, wall means surrounding said lumen,and aperture means for entry of a pressure medium into the lumen.

Intracoronary pressure recordings give valuable information to thecardiologist to assess both coronary and myocardial flow reserve andcollateral blood flow.

The problem of pressure measuring guide wires is to provide anuninterrupted lumen throughout the shaft which has to be highly flexibleto conform with the tortuous pathways of the blood vessels;simultaneously, the shaft must have a reasonably high stiffness toassure pushability and torque transmission thereto; and furthermore, theshaft must have a very good kink resistance to avoid the risk ofconstrictions resulting in modification of the advance of pressure wavesthrough the lumen.

Current pressure measuring guide wires are made of a plastic tube and astiffening wire. This is, however, very costly and leads toconstrictions in the lumen which obstruct the advance of pressure wavesin the lumen.

Another approach is shown in the document EP-A1-0419277 which describesa guide wire for use in measuring a characteristic of liquid flow in avessel comprising a flexible elongate element in the form of a tube witha core wire provided therein the distal extremity of which is taperedand extends beyond the distal end of the tube. The tapered extremity ofthe core wire extends into a coil spring which is soldered to the tube.The coil spring is formed of two parts which are screwed together andthe spring is bonded to the core wire by solder at the region where thetwo portions of the coil spring are screwed together. A safety wireextends from the joint of the two coils to the distal extremity of thecoil spring where it is secured to a transducer carried by the distalend of the coil spring. Front and rear contacts are provided on thetransducer and are connected to a two conductor wire which extendsrearwardly and interiorly of the coil spring and further extends intothe tube between the core wire and the interior of the tube to get outof the tube for connection to a male connector. According to a variant,an insulating sleeve may form a tight fit with the exterior surface ofthe core wire and it may also fit within the tube to insulate the corefrom the tube so that the core and the tube and core may serve asseparate and independent electrical conductors.

It is an object of this invention to improve over the cited art by meansof a pressure measuring guide wire which is easy and inexpensive tomanufacture, which is highly versatile while having excellent qualitiesof pushability and resistance to kinking, and which allows a smoothadvance of pressure waves through the lumen.

SUMMARY OF THE INVENTION

Towards fulfilling of these and other objects, the invention providesfor a pressure measuring guide wire comprising an elongated flexibleshaft with a proximal area, a distal area, a lumen extending through theshaft, wall means surrounding said lumen, and aperture means for entryof a pressure medium into the lumen, wherein said wall means have afirst portion of length having a first resistance to kinking, a secondportion of length having a second resistance to kinking, said secondresistance to kinking being smaller than said first resistance tokinking, and wherein coil means are supporting said second portion oflength. Accordingly, it becomes possible to modulate the resistance tokinking as a function of the structural organization for the pressuremedium entry into the lumen. The wall thickness may be selected at will,whereby the shaft can be made flexible and stiff enough to be pushed.The resistance to kinking can be practically constant and the risk ofconstrictions due to kinking is eliminated. A stiffening wire is no moreneeded, and there is a better frequency behaviour for the fluid medium.

The first portion of length or the second portion of length may be inthe distal area of the shaft, making it possible to select at will theconfiguration of the supporting coil means.

Where the first portion of length has a first thickness and the secondportion of length a second thickness smaller than the first one, withthe first portion of length having a plurality of slots formed thereinfor entry of the pressure medium, the mere choice of thickness allowsmastering the difference in resistance to kinking due to the presence ofthe slots.

Within this frame, the first portion of length may have a first outerdiameter and the second portion of length may have a second outerdiameter smaller than the first outer diameter, whereby the coil meansmay surround the second portion of length. In this configuration, thecoil means and diameters may be easily chosen to have the coil means inflush alignment with the first outer diameter, for having an overallouter diameter constant and reduced friction upon travelling through theblood vessels. And to assure simple positioning of the coil means on thesecond portion of length, this second portion of length may be precededproximally by a third portion of length having a third outer diameterlarger than said second outer diameter, with the coil means surroundingthe second portion of length between said first and third outerdiameters. In that configuration the coil means may also be in flushalignment with the first outer diameter for the same reason of diameterconstancy and friction reduction.

Still within this frame, the first portion of length may have a firstinner diameter and the second portion of length may have a second innerdiameter larger than the first inner diameter, whereby the coil meansmay be located within the second portion of length. In thisconfiguration, the coil means and diameters may also be easily chosen tohave the coil means in flush alignment with the first inner diameter forhaving an overall outer shaft surface which is homogeneous while theinner diameter of the shaft remains constant.

In any of the arrangements with the first portion of length in thedistal area of the shaft and with slots formed in the first portion oflength, some of the slots may be proximal of the first portion of lengthwith some other slots being distal of the first portion of length,thereby avoiding too many holes on the same diameter in order tominimize the risk of kinking resistance reduction in that area.

Where the second portion of length has a plurality of elongated slotsformed therein for entry of the pressure medium and the coil means arelocated inside the shaft and extend at least under the slots, a verysmall thickness of the wall may be achieved all along the shaft,including the weakened area of slot location which is supported by thecoil means which avoids the risk of kinking in that delicate area. Andas the slots are fully supported by the coil means, they can be locatedat the same level along the second portion of length. To facilitateentry of the pressure medium, the coil means may have adjacent windingswhich are spaced apart from one another extending at least under theslots.

In order to stiffen the coil means without interfering with the shaft,core means may extend through the coil means. Where such core means havea proximal portion for longitudinal abutment against a proximal end ofthe coil means and a distal portion for longitudinal abutment with adistal end of the coil means, a stress free assembly is achieved whichstiffens the turns of the coil means and which leaves the shaft lumenfree of any obstruction proximally of the coil means. The core means mayalso have their proximal portion integral with a wire which extendsproximally along and out of the lumen of the shaft. In that case, thesupporting coil may be placed under the slots only for insertion of theguide wire to assure the required resistance to kinking. Duringinsertion, the wire extending the core also has some stiffening effectfor the shaft and improves its pushability. When the guide wire isproperly located, the wire and supporting coil are removed from theguide wire to have the shaft lumen fully free of obstruction forpressure measurements.

In sum, the present invention relates to a pressure measuring guide wirehaving an elongated flexible shaft with a proximal area, distal area, alumen extending through the shaft, wall means surrounding the lumen, andaperture means for entry of a pressure medium into the lumen. The wallmeans may have a first portion of length having a first resistance tokinking, and a second portion of length having a second resistance tokinking, the second resistance to kinking being smaller than the firstresistance to kinking, and coil means supporting the second portion oflength. The first portion of length may be in the distal area of theshaft. The second portion of length may be in the distal area of theshaft. The first portion of length may have a first thickness and thesecond portion of length may have a second thickness smaller than thefirst thickness, and the first portion of length may have a plurality ofslots formed therein. The first portion of length may have a first outerdiameter and the second portion of length may have a second outerdiameter smaller than the first outer diameter, and the coil means maysurround the second portion of length. The second portion of length maybe preceded proximally by a third portion of length having a third outerdiameter larger than the second outer diameter, and the coil means maysurround the second portion of length between the first and third outerdiameters. The coil means may be in flush alignment with the first outerdiameter. The first portion of length may have a first inner diameterand the second portion of length may have a second inner diameter largerthan the first inner diameter, and the coil means may be located withinthe second portion of length. The coil means may be in flush alignmentwith the first inner diameter. Some of the slots may be proximal of thefirst portion of length and some other slots may be distal of the firstportion of length. The second portion of length may have a plurality ofelongated slots formed therein, and the coil means may be located insidethe shaft and extend at least under the slots. The elongated slots maybe located at the same level along the second portion of length. Thecoil means may have adjacent windings which are spaced apart from oneanother, and extending at least under the slots. The pressure measuringguide wire may further have core means extending through the coil means,which may have a proximal portion for longitudinal abutment against aproximal end of the coil means, and a distal portion for longitudinalabutment with a distal end of the coil means. The proximal portion ofthe core means may be integral with a wire which extends proximallyalong and out of the lumen of the shaft. The shaft may be made of anelastic nickel titanium alloy, and the coil means may be made of highdensity metal such as tungsten. The distal area of the shaft mayterminate in helical coil means defining a flexible assembly having adistal portion terminating into a tip. The helical coil means may bemade of high density metal.

DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention willbecome readily apparent from the following detailed description withreference to the accompanying drawings which show, diagrammatically andby way of example only, three embodiments of the invention.

FIG. 1 is a cross sectional view of the first embodiment.

FIG. 2 is a cross sectional view of the second embodiment.

FIG. 3 is a cross sectional view of the third embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

The guidewire shown in FIG. 1 comprises an elongated flexible shaft 1having a distal area 2 and a proximal area 3. A lumen 4 extends throughthe shaft 1, and the proximal area 3 of the shaft is intended to beconnected to a pressure measuring and monitoring equipment (not shown)common in the art.

Preferably, the shaft 1 is made of an elastic nickel titanium alloy suchas for instance Nitinol™ or Tinel Alloy™. Other materials are alsopossible, for instance plastic materials.

The lumen 4 is surrounded by a wall 5 forming the shaft 1 and having afirst portion of length 6 and a second portion of length 7. The firstportion of length 6 is located in the distal area 2 of the shaft 1 andit has a first thickness 8; the second portion of length 7 is located inthe proximal area 3 of shaft 1 and it has a second thickness 9, smallerthan the first thickness 8, thereby achieving a resistance to kinkingwhich is smaller than that of the first portion of length 6. Thedifference in thickness results from the fact that the first portion oflength 6 has an outer diameter 11 longer than the diameter 12 of thesecond portion of length 7.

The first portion of length 6 has a plurality of slots 10 formed thereinfor entry of the pressure medium; some of these slots 10 are proximal ofthe first portion of length 6 and some other of these slots are distalof the first portion of length 6.

A coil 13, preferably of a high density metal such as for instancetungsten, is mounted on the second portion of length 7 for supportingpurposes. This high density metal coil also provides a radiopaquereference for the first portion of length 6. This coil 13 is in flushalignment with the outer diameter 11 of the first portion of length 6.

The second portion of length 7 is preceded proximally by a third portionof length 14 of wall 5 having an outer diameter 15 greater than thesecond diameter 12, in the example shown, equal to the first outerdiameter 11. The coil 13 is thus comprised between the first diameter 11and the third diameter 15.

The distal area 2 of shaft 1 terminates in a flexible assembly 16comprising a coil 17, preferably made of a high density metal such astungsten, which also provides a radiopaque reference for the firstportion of length 6 which is thus easily locatable between the tworadiopaque references provided for by coils 13 and 17. The coil 17 abutsproximally on the distal end 18 of shaft 1 and its distal extremityterminates into a tip 19. A cylindrical core 20, for example ofstainless steel, has its proximal portion 21 affixed, for instancewelded, into the distal end 18 of shaft 1; core 19 tapers into aflattened straight and narrow distal portion 22 which terminates bywelding into the tip 19.

The guide wire shown in FIG. 2 also comprises an elongated flexibleshaft 31 having a distal area 32 and a proximal area 33. A lumen 34extends through the shaft 31, and as for the embodiment of FIG. 1 theproximal area 33 of the shaft 31 is intended to be connected to apressure and monitoring equipment (not shown).

Preferably, the shaft 31 is also made of an elastic nickel titaniumalloy such as Nitinol™ or Tinel Alloy™, but other materials such asplastic materials are also possible.

The lumen 34 is surrounded by a wall 35 forming the shaft 31 and havinga first portion of length 36 and a second portion of length 37. Thefirst portion of length 36 is located in the proximal area 33 of shaft31; the second portion of length 37 is located in the distal area 32 ofshaft 31 and it has a plurality of elongated slots 38 formed therein forpressure medium entry, thereby achieving a resistance to kinking whichis smaller than that of the first portion of length 36 which is devoidof slots. The slots 38 may be located at the same level along the secondportion of length 37, as shown.

A coil 39, preferably of a high density metal such as for exampletungsten, is located inside the shaft 31 under the slots 38 forsupporting the wall and slot structure and for providing a radiopaquereference for the second portion of length 37. This coil 39 extendssomewhat beyond the slots 38 and, as shown, it may have adjacentwindings which are spaced apart from one another to facilitate entry ofthe pressure medium within the lumen 34.

A core member 41, preferably in stainless steel, is located within thecoil 39. This core member 41 has a proximal portion 42 in the form of atruncated cone for longitudinal engagement with the proximal end of thecoil 39, and a distal portion 43 which is flattened so that theresulting enlargement abuts longitudinally against the distal end of thecoil 39.

The distal area 32 of shaft 31 terminates in a flexible assembly 44, asdescribed in European Patent Application No. 95103006.3 filed Mar. 2,1995, comprising a first coil 45 having a proximal portion 46 and adistal portion 47, and a second coil 48 having a proximal portion 49 anda distal portion 50 ending in a weld tip 51. The proximal portion 46 offirst coil 45 comprises adjacent windings which are spaced apart andthis proximal portion 46 is threadedly force fitted into the tubulardistal area 32 of shaft 31. An adhesive may be injected between thewindings of proximal portion 46 of coil 45. This first coil is made of ahigh density metal, preferably tungsten, to provide a radiopaquereference for the flexible assembly 44. The second coil 48, also made ofa high density metal such as tungsten, has its proximal portion 49threadingly surrounding the distal portion of first coil 45 and abuttingagainst the distal end of shaft 31. A cylindrical core 52, preferably ofstainless steel, extends through the coil 45 and has a proximal portion53 flattened so that the resulting enlargement abuts longitudinallyagainst the proximal end 46 of coil 45. The core 52 tapers into aflattened straight and narrow portion 54 which terminates by weldinginto the tip 51.

The guide wire shown in FIG. 3 comprises the same integers andcorresponding reference numerals as the guide wire of FIG. 2.Additionally, core 41 has its truncated cone proximal portion 42integral with the distal end of a wire 60 which extends along lumen 34up to the proximal end of shaft 31 where it can be grasped for takingthe assembly of core 41 and coil 39 out of the shaft 31. Accordingly,the coil 39 may be placed and maintained under the slots 38 only forinsertion of the guide wire and withdrawn from the guide wire forpressure measuring.

Variants are available without departing from the scope of theinvention.

For instance, the flexible assembly 16 of the first embodiment of FIG. 1may be replaced by the flexible assembly 44 of the embodiment of FIG. 2and vice versa.

The second portion of length 7 of the embodiment of FIG. 1 may have aninner diameter which is larger than the inner diameter of the firstportion of length 6, whereby the coil 13 may be located inside thesecond portion of length 7, preferably in flush alignment with the innerdiameter of the first portion of length.

I claim:
 1. A pressure measuring guide wire comprising an elongatedflexible shaft with a proximal area, distal area, a lumen extendingthrough the shaft, wall means surrounding said lumen, and aperture meansfor entry of a pressure medium into the lumen, wherein said wall meanshave a first portion of length having a first resistance to kinking, asecond portion of length having a second resistance to kinking, saidsecond resistance to kinking being smaller than said first resistance tokinking, and wherein coil means are supporting said second portion oflength.
 2. A pressure measuring guide wire according to claim 1, whereinsaid first portion of length is in the distal area of the shaft.
 3. Apressure measuring guide wire according to claim 1, wherein said secondportion of length is in the distal area of the shaft.
 4. A pressuremeasuring guide wire according to claim 2, wherein said first portion oflength has a first thickness and said second portion of length has asecond thickness smaller than said first thickness, and wherein saidfirst portion of length has a plurality of slots formed therein.
 5. Apressure measuring guide wire according to claim 4, wherein said firstportion of length has a first outer diameter and said second portion oflength has a second outer diameter smaller than said first outerdiameter, and wherein said coil means surrounds said second portion oflength.
 6. A pressure measuring guide wire according to claim 5, whereinsaid second portion of length is preceded proximally by a third portionof length having a third outer diameter larger than said second outerdiameter, and wherein the coil means surrounds the second portion oflength between said first and third outer diameters.
 7. A pressuremeasuring guide wire according to claim 5, wherein the coil means is inflush alignment with said first outer diameter.
 8. A pressure measuringguide wire according to claim 4, wherein said first portion of lengthhas a first inner diameter and said second portion of length has asecond inner diameter larger than said first inner diameter, and whereinsaid coil means is located within said second portion of length.
 9. Apressure measuring guide wire according to claim 8, wherein the coilmeans is in flush alignment with said first inner diameter.
 10. Apressure measuring guide wire according to claim 4, wherein some of saidslots are proximal of said first portion of length and some other slotsare distal of the first portion of length.
 11. A pressure measuringguide wire according to claim 3, wherein said second portion of lengthhas a plurality of elongated slots formed therein, and wherein said coilmeans is located inside the shaft and extend at least under said slots.12. A pressure measuring guide wire according to claim 11, wherein saidelongated slots are located at the same level along said second portionof length.
 13. A pressure measuring guide wire according to claim 11,wherein said coil means has adjacent windings which are spaced apartfrom one another, said spaced apart windings extending at least underthe slots.
 14. A pressure measuring guide wire according to claim 11,further comprising core means extending through the coil means.
 15. Apressure measuring guide wire according to claim 14, wherein said coremeans has a proximal portion for longitudinal abutment against aproximal end of said coil means, and a distal portion for longitudinalabutment with a distal end of said coil means.
 16. A pressure measuringguide wire according to claim 15, wherein the proximal portion of thecore means is integral with a wire which extends proximally along andout of the lumen of the shaft.
 17. A pressure measuring guide wireaccording to claim 1, wherein the shaft is made of an elastic nickeltitanium alloy.
 18. A pressure measuring guide wire according to claim1, wherein said coil means is made of high density metal.
 19. A pressuremeasuring guide wire according to claim 18, wherein the coil means ismade of tungsten.
 20. A pressure measuring guide wire according to claim1, wherein the distal area of the shaft terminates in helical coil meansdefining a flexible assembly having a distal portion terminating into atip.
 21. A pressure measuring guide wire according to claim 20, whereinsaid helical coil means is made of high density metal.
 22. A guidewirefor use in pressure measurement, the guidewire comprising:(a) anelongate flexible assembly having an outer surface therealong and alumen extending at least partially therethrough, the assembly having:(i)a first coil against the outer surface for supporting a first length ofthe assembly; (ii) a second coil supporting a second length of theassembly, the second coil against the outer surface and spacedproximally from the first coil in a non-overlapping configuration; and(iii) openings in the outer surface to allow the passage of pressurizedfluid into the lumen.
 23. A guidewire for use in pressure measurement,the guidewire comprising:(a) an elongate flexible assembly having anouter surface and a lumen extending at least partially therethrough, theassembly having:(i) a first coil against the outer surface forsupporting a first length of the assembly; (ii) a second coil againstthe outer surface for supporting a second length of the assembly, thesecond coil spaced proximally from the first coil in a non-overlappingconfiguration; and (iii) openings in the outer surface disposed betweenthe first and second coils to allow the passage of pressurized fluidinto the lumen.
 24. A guidewire for use in pressure measurement, theguidewire comprising:(a) an elongate flexible assembly having an outersurface and a lumen extending at least partially therethrough, theassembly having:(i) a first coil against the outer surface forsupporting a first length of the assembly; (ii) a second coil againstthe outer surface for supporting a second length of the assembly, thesecond coil spaced proximally from the first coil in a non-overlappingconfiguration; and (iii) openings in the outer surface disposed aboutthe second coil to allow the passage of pressurized fluid into thelumen.